Process of making nitric acid and other products.



F. S WASHBURN.

PROCESS OF MAKING NITRIC ACID AND OTHER PRODUCTS.

APPLICATION FILED MAY 6, 1916.

'1 06,063. Patented Nov. 28, 1916.

Ennkfif .T V ashburm, by

FRANK s; WASHBURN, or NEW Yonx, N. Y.

PROCESS or MAKINGYNITRIC ACID AND OTHER PRODUCTS.

Specification of Letters Patent.

. Patented Nov. 28, 1916.

Original application filed February 7, 1916, Serial No. 76,647. Divided and this application filed May 6,.

1916. Serial No. 95,896.

useful Improvements in Processes ,of- Making Nitric Acid and other Products; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable other skilled in the art to which it appertains to make and use the same.

This invention relates to a process of treating ammonia in such a manner as to produce a highly concentrated nitric acid simultaneously with other useful ammonia salts, and has for its object to provide a means and a method that will obviate the inherent difficulties in the processes heretofore proposed, while enabling one to operate more efiiciently and economically.

With these and other objects in view, the invention consists in the novel combinations of steps constituting the process as will be more fully hereinafter disclosed and particularly pointed out in the claims.

This application is a division of my prior application Serial Number 76,647, filed February 7, 1916, and entitled Process of and apparatus for making nitric acid and other products.

In the well known processes of oxidizing ammonia it has long been recognized that when subjecting the ammonia and oxygen containing mixture to the influence of a suitable catalyzer, a simultaneous oxidation of the ammonia to nitrose gases and a decomposition of these nitrose gases to nitro-.

gen gas takes place. It is, therefore, well recognized that one must So control these simultaneous reactions that the velocit of the oxidation reaction is very materially greater than the velocity of the decomposition reaction, for otherwise one will decompose too much of the nitrose gases to enable a commercially practicable process to result.

In one of the prior processes the relative velocities of these two simultaneously occurring reactions are controlled by so ad:

justing the size of the catalyzing mass and the velocity of the gases passing through it, that all the ammonia is either oxidized or decomposed, and none gets past in the form of free ammonia. But the control of the velocity of such gases, particularly ammonia, is very comphcated and difficult, for it is influenced to a considerable extent by the relative quantities of ammonia and oxygen contained in the mixture, as well as by the actual rate at which the gas passes the catalyzer. In practice it is not only diflicult to maintain the desired uniform mixture containing the right proportions of ammonia and oxygen but even with a carefully designed catalyzer, it is almost impossible to pass every portion of this mixture atexactly the ri ht rate uniformly, over every portion of the catalyzer, so that no free ammonia escapes through without I suffering a decompositionor an oxidation. Accordingly, this said prior process, on the average, has been forced to operate somewhat below its maximum rate, in order to avoid obtaining free ammonia with the product. Further when operating said prior process in practice, it is found that the decomposition by the catalyzer of the nitrose gases becomes quite serious and it is safe to assume that its efficiency of oxidation of the ammonia, is probably notover 75% to 85%.

On the other hand, according to the in vention now to be disclosed, it involves no serious inconvenience if the mixture containing ammonia and oxygen be passed at Such a rate over or through the catalyzer that free ammonia appears'in the products of the reaction. But one, of course, should avoid passing said mixture at such a rate as to produce a very large excess of ammonia, for in that case other difliculties will result as will,

be now explained. That is to Say, technical diiiiculties in designing and operating the oxidizing apparatus prohibit the employ- 'ment of such a speed in the mixture passing in the colder portions of the apparatus, and clog them up so it is only by Operating very skilfully in such cases that one can practically carry out the direct production of ammonium nitrate in this way. It is, however, very convenient to permit say 5% to 15% of the ammonia fed to the catalyzer to pass through undecomposed, and it is with such relative smaller quantities of free ammonia, that I prefer to operate.

In carrying out this invention I prefer to pass this free ammonia along with the nitrose gases through a suitable cooler and into an oxidation tower, when with a properly designed apparatus, a very large proportion of that passing the catalyzer can be kept from decomposition, and passed intothe oxidation and absorption towers as free ammonia, where it combines with the nitric and nitrous acids formed and finally appears as ammonium nitrate. dissolved with dilute nitric acid. This dilute nitric acid is next concentrated by a suitable means.

But a concentration by means of any of the well known sulfuric acid processes, converts this ammonium nitrate into ammonium sulfate and nitric acid, which acid can be recovered as such; and when the sulfate has accumulated to a suitable concentration, it of itself, will precipitate out, and is recovered from the sulfuric acid in the usual and well known manner. As an alternative method I may so operate that I permit free ammonia to pass the catalyzer and form ammonium nitrate dissolved in nitric acid as above described and I then saturate the excess of nitric acid with ammonia from an outside source so as to produce from my oxidation apparatus ammonium nitrate as its sole product. This solution can be readily evaporated and crystallized, thus producing a dry ammonium nitrate which can be marketed as such, or employed in many industries.

In case I do not desire to market the arm mum velocity of the nitrose gas decomposition, referred to above, so in such case, I obtain a very much higher efficiency of oxidation of the ammonia with considerably less decomposition of either the ammonia orv of the nitrose gases, than is the case Where I so limit the velocity of these gases through 'or over the catalyzer to such an extent that no ammonia appears in the products of the oxidation as such. It therefore follows that by observing the quantity of free ammonia that passes the catalyzer, I am enabled to judge the real efficiency of the chemical reaction that is -going on. In fact, it is a comparativcly simple matter to oxidize ammonia by this system at an elliciency far above 90% if proper account is taken of the undecomposed ammonia passing the catalyzer.

In carrying out the process, I prefer to use a mixture of predetermined proportions of ammonia and oxygen, of ammonia air and oxygen or of ammonia and air, and to precool the same all in a manner similar to that disclosed in the copending application of lValter S. Landis, filed Feb. 15, 1915, Serial No. 9595, and entitled Method of and apparatus for oxidizing ammonia.

In order that the invention may be the more clearly understood, reference is had to i the accompanying drawing forming a part of this specification, in which the figure is a diagrammatic partially sectional, partially elevational view of an apparatus suitable for carrying out the process.

Referring to the said drawing, 1 indicates any suitable conduit for supplying the ammonia mixture to be oxidized; 2 a valved connection leading from said conduit to the oxidizing chamber 3. Located in the chamber 3 is any suitable form of cooler 4 adapted to cool the gaseous mixture before reaching the catalyzer 5, or to screen the oncoming stream of ammonia from the heat radiated from said catalyzer. The catalyzer may be of any suitable material, but I prefer iridium free platinum of a uniform cross section in order that it may be uniformly heated by an electric current.

After the gaseous mixture passes the catalyzer 5 it will be found to contain the oxide of nitrogen mixed with ammonia, water vapor and free nitrogen, if air was originally employed, and this mixture passes through the valved connections 6 to the conduit 7,

thence preferably through a cooler 8, having a coil 9 and a supply 10 for a cooling medium.

From the cooler 8, the said mixture is conveniently passed through a suitable absorption tower 11 which may be supplied with ents, it may be repeatedly circulated through 19, tank 20 and valved connection 21, the unabsorbed gases in all cases escaping from tower 11, through the pipe 22. If the tower 11 is so designed as to absorb all the ammonia and nitrose gases delivered to it, then the other gases contained in the mixture may be led to waste through said pipe 22. But in those cases, where it is less expensive to run the said nitrogen containing gases through a plurality of towers, in order to absorb all the combined nitrogen the said pipe 22 is led to one or more additional towers such as 25, from which the waste gases escape through the pipe 26.

The tower 25 may ,be conveniently supplied with water through theupipe 27, and connected with the tank 20 through the pipe 28. nium nitrate formed in said tower 25 may be conveniently delivered through the connection to the tank 31, from which it may be drawn off by means of the valved connections 32, 15 and 16 when desired, or when said solution is found to be too weak for drawing off it may be repeatedly cir culated back through said tower 25, by means ofthe pump 18, pipe 19, tank 20 and connection 28. A valved pipe permits the contents of the tank 31 to be emptied at will into the tank 14:.

When it is desired to convert all the nitric acid into ammonium nitrate free ammonia may be led to the tower 11 through the valved pipe 40.

It is obvious that. those skilled in the art may vary the details of both the process and apparatus without departing from the spirit The solution of nitric acid and ammoof the invention, and therefore I do not wish to be limited to the above disclosure except as may be required by the claims.

What I claim is 1. The process of producing nitric acid and ammonium sulfate, which consists in subjecting a mixture of ammonia and oxygen containing gases to the action of a catalyzer and at such arate as to cause free ammonia and nitrose gases to appear in the products of the reaction; producing a solution of nitric acid and ammonium nitrate from said products; concentrating said solution; and treating the ammonium nitrate in said solution with sulfuric acid to concentrate the nitric acid present and to form ammonium sulfate, substantially as described.

2. The process of producing nitric acid and ammonium sulfate, which consists in subjecting a mixture of ammonia and oxygen containing gases to the action of a catalyzer and at such a rate as to cause nitrose gases and not exceeding 20% of free ammonia to appear in the products of the reaction; producing a solution of nitric acid and ammonium nitrate from said products; concentrating said solution; and treating the ammonium nitrate in said solution-With sulfuric acld to concentrate the nitric acid present and to form ammomum'sulfate, substantially as described.

In testimony whereof I aflix my signature, in presence of two witnesses.

FRANK s. WASHBURN.

Witnesses:

BRUNO DELANY, G. N. SGHUMAN. 

